Electrical key switching device



y 21, 1942- I R. F. STEHLIK I 2,290,453

ELECTRICAL KEY SWITCHING DEVICE Filed May 18, 1958 2 Sheets-Sheet 1 INVENTOR'. RUDOLPH FRANK STE/{L/K ATTORNEY.

July 21, 1942.

r, R. F. STEHLJK 2,290,453

ELECTRICAL KEY SWITCHING DEVICE Filed May 18, 1939 2 Sheets-Sheet 2 INVENTOR: RUDOLPH FRANK STEI-lL/K ATTORNEY.

Patented 'July 21, 1942 ELECTRICAL KEY SWITCHING DEVICE Rudolph Frank Stehlik, Antwerp, Belgium, as-

signor to Associated Telephone & Telegraph Company, Chicago, 111., a corporation of Delaware Application May 18, 1939, Serial No. 274,385 In Great Britain May 26, 1938 4 Claims.

The present invention relates to electrical key switching devices of the type which find considerable application in telephone systems, and its chief object is to simplify and cheapen the construction of such keys while rendering their action more reliable.

According to the invention in a switching key for controlling electric circuits the operating member normally engages a spring-controlled intermediate member which is arranged to have an appreciable movement before effecting the operation of any contact springs.

The invention Will be better understood from the following description of one method of carrying it into effect which should be taken in conjunction with the accompanying drawings comprising Figs. 1-8.

Figs. 13 show two elevations and a plan of the complete key.

Figs. 4 and 5 illustrate the upper portion and show how the special blocking member may be connected in its alternative positions.

Fig. 6 shows in greater detail the frame members from which the key is built up, and

Figs. 7 and 8 show two views of the operating member or handle.

Referring first to Figs. 7 and 8, the operating member is preferably moulded in one piece from material of the synthetic resin type and is of the shape shown. It consists of a handle portion I, a

bulbous portion 2 having a central hole through which the pivot pin 3 passes, and a lower cam portion 4 which is preferably symmetrical and provided with two depressions 5.

The main frame of the key shown in Fig. 6 is made up of two identical members 6 and I each of which forms one half of the bearing for the pivot pin 3. These two portions 6 and I are secured together by rivets 8 and 9 and are provided with raised portions I 0 and I I on which the two groups of contact springs I2 and I3 are mounted as shown in greater detail in Figs. 1 and 2. The contact springs are secured to the portions I0 and II by screws I4 engaging clamping plates I5, I6 and I! which are of channel section, This construction gives the necessary rigidity While reducing the space occupied since the heads of the clamping screws I4 do not project beyond the sides of the channel. The operating member I is retained in position by the escutcheon plate I8 which is secured to the frame member by the screws I 9.

Each contact spring unit is operated by an intermediate member such as 20 and 2| which is mounted on a thin spring 22, 23 secured in the contact pile. The intermediate member 21 carries a roller 24 arranged to engage in the depression 5 in cam portion 4 of the operating member. It will be realised that when the key handle I is thrown to the left the roller 24 rides up on the projecting portion of the cam surface 4 and since it has then no tendency to return the key remains in this position so that a looking effect is produced. Moreover when the key is restored to normal the roller 24 by engaging in the depression 5 prevents any overthrow and thus provides an anti-click feature.

It will be seen that when the roller 24 rides on the cam portion 4 the intermediate member 2| is moved to the right and after a slight amount of lost motion engages the buffer 25 thus operating the spring set I 3. A similar effect is produced on the spring set I2 if the handle I is thrown to the right. It will be appreciated that the cam portion between the two depressions 5 is considerably higher than the portions on the opposite sides of the depressions so that when the handle I is moved to the left, there is only a slight movement of the left-hand intermediate member 20 insufficient to operate its contact springs.

Figs, 4 and 5 show the effect of adding the blocking member 26 which can be secured by either of the screws I9. \Vhen the member 26 is employed in the position shown in Fig. 4 it engages the edge of the cam portion 4 of the operating member and thus prevents the handle I being thrown to the left. Consequently the key only has one operating and one normal position. If however the member 26 is reversed so as to be connected up in the position shown in Fig. 5, the handle I can be operated to the left but not fully, so that the roller 24 does not ride completely out of the depression 5 and thus when the handle is released the key returns to normal. This arrangement accordingly gives a two-position key with one position locking and one nonlocking. Clearly if the blocking member 26 is removed entirely, there is no restriction on the movement of the handle and the key becomes a two-position key locking in both directions.

According to the invention therefore a very simple construction of switching key has been evolved which permits various types to be constructed from a minimum number of parts and gives improved reliability of operation.

I claim:

1. In a switch key, a support, a rotary cam mounted on said support and having a normal position with respect thereto, two cam followers resting respectively in two depressions in said cam when same is in its normal position, both of said cam followers operated by said cam whenever same is rotated in either direction from its normal position and each of said cam followers effective independently of the other cam follower to exert a restoring force upon the cam whenever same is rotated in either direction from its normal position, a set of contact springs individual to one cam follower, means controlled by said one cam follower to operate said spring set only when the cam is rotated in one direction from its normal position, another set of contact springs individual to the other cam follower, and means controlled by said other cam follower to operate said other spring set only when the cam is rotated in the other direction from its normal position.

2. In a switch key, a support, an operating cam mounted for rotation on said support, said cam having three projections spaced apart from one another by two depressions, the central one of said projections extending farther from the center of rotation of the cam than the other two projections, said cam having a normal position and adapted to be rotated in either direction therefrom at will, two cam followers positioned respectively in the two said depressions of said cam when same is in its normal position, and a set of contact springs individual to each cam follower and operated thereby only when the cam is operated in such a direction as to bring said central projection under that cam follower.

3. In a switch key, contact springs, a support,

pivotally mounted on said support for movement in either direction from a central position, said member efiective whenever moved a certain distance in either direction from said central position to remain in its operated position until a manual restoring force is applied, means for automatically restoring said member to its central position whenever said member is moved therefrom less than said certain distance, an auxiliary member having an offset lug, means for mounting said auxiliary member variably at a particular point on said support so that said lug may occupy either of two positions with respect to said support, said lug effective when in one of said two positions to substantially prevent said operating member from being moved in one direction from its central position, and said lug effective when in the other of said two positions to limit the movement of said operating member in one direction thereby to permit same to be moved sufliciently in that direction to operate certain of said contact springs but not enough to cause same to remain in its operated position until a manual restoring force is applied.

4. In a switch key, a frame comprising a pair of plates lying parallel and fastened flatl together throughout a portion of their length, said plates having their end portions bent away from one another to make the frame substantially Y- shaped, the end portion of each plate having a lug formed integrally therewith and bent at right angles to said end portion so that the two lugs are substantially parallel and spaced apart from one another, contact springs mounted on said frame, an operating lever for said springs, and means for mounting said lever pivotally upon an operating member for said contact springs and between said two lugs.

RUDOLPH FRANK STEHLIK. 

